In W-CDMA (Wideband Code Division Multiple Access), a mobile station performs cell search by means of a downlink physical channel referred to as a SCH (Synchronization Channel). The SCH includes two subchannels: a P-SCH (Primary SCH) and an S-SCH (Secondary SCH) (see “W-CDMA MOBILE COMMUNICATIONS SYSTEM” edited by Keiji Tachikawa, Japan, Mar. 15, 2002, page 112).
The P-SCH is used by the mobile station to detect slot timing. The S-SCH is used by the mobile station to detect frame timing and a scrambling code group (spreading code group). The mobile station achieves fast cell search by means of these two SCHs.
The P-SCH signal and the S-SCH signal are code-multiplexed in the time domain for transmission. The mobile station despreads the P-SCH signal and the S-SCH signal and separates them. Since the P-SCH signal and the S-SCH signal are code-multiplexed and transmitted at the same timing, they experience the same channel fluctuations. Accordingly, the mobile station can perform synchronous detection of the S-SCH signal using the detected P-SCH signal as a reference signal (pilot signal) upon correlation detection of the S-SCH signal. In this manner, the S-SCH signal is detected with high accuracy.